The present invention relates to a cleaning apparatus for cleaning an outer surface of a rotary member by pressing a cleaning web against it and, more particularly, to a catching detecting method and unit in the cleaning apparatus which detect that a cleaning web is caught in a rotary member.
In general, a printing press has a cleaning apparatus for cleaning the outer surface of a cylinder serving as a rotary member by urging a belt-like cleaning cloth against it. EP 0552856 (reference 1) discloses a cleaning apparatus of this type, the main part of which is shown in FIG. 11. Referring to FIG. 11, reference numeral 1 denotes the blanket cylinder of the printing press. A supply shaft 2 supplies a belt-like cleaning cloth 6. A take-up shaft 3 takes up the cleaning cloth 6. Guide rollers 4 and 5 guide the cleaning cloth 6 to the outer surface of the blanket cylinder 1. A lever 8 is axially supported by a support pin 7 and detects that the cleaning cloth 6 is caught. A tension spring 11 has two ends respectively fixed by spring catches 9 and 10. A limit switch 12 is actuated by the lever 8.
The take-up shaft 3 intermittently takes up the cleaning cloth 6 supplied from the supply shaft 2 through the guide rollers 4 and 5. In this cleaning apparatus, the cleaning cloth 6 intermittently traveling between the supply shaft 2 and take-up shaft 3 is pressed against the rotating blanket cylinder 1 in a taught state, so the outer surface of the blanket cylinder 1 is cleaned with it. At this time, since the blanket cylinder 1 is rotating, the cleaning cloth 6 might be caught in the blanket cylinder 1 during cleaning. In other words, the cleaning cloth 6 may adhesively attach to the blanket surface of the blanket cylinder 1 due to the viscosity of the ink, or may be torn up by some causes, so the cleaning cloth 6 is accidentally caught in the rotating blanket cylinder 1.
In this case, in a conventional cleaning apparatus, the accident in which the cleaning cloth 6 is caught is detected in the following manner. When the cleaning cloth 6 is not caught, a distal end 8b of the lever 8 is pressed by the traveling cleaning cloth 6 because of the biasing force of the tension spring 11, and the limit switch 12 is set in the non-operative state. When the cleaning cloth 6 is caught, the cleaning cloth 6 is loosened, so the lever 8 is rotated clockwise in FIG. 11 by the biasing force of the tension spring 11. A distal end 8b of the lever 8 then presses an actuator 12a of the limit switch 12 to turn on an internal contact.
In the above cleaning apparatus, the limit switch 12 detects that the lever 8 swings in accordance with a change in tension of the cleaning cloth 6. Hence, when the cleaning cloth 6 is caught, if the tension of the cleaning cloth 6 does not change, accidental catching of the cleaning cloth 6 cannot be detected.
It is an object of the present invention to provide a cleaning apparatus which can reliably detect catching of a cleaning cloth even if the tension of the cleaning cloth does not change, and a method of detecting catching of the cleaning web in this apparatus.
In order to achieve the above object, according to the present invention, there is provided a cleaning apparatus comprising a cleaning web pressed against a rotary member and adapted to clean an outer surface of the rotary member, a supply shaft around which the cleaning web before cleaning is wound and which rotates in accordance with supply operation of the cleaning web to the outer surface of the rotary member, a take-up shaft rotatably driven to take up the cleaning web supplied from the supply shaft to the outer surface of the rotary member, signal output means for outputting a signal corresponding to a rotational speed of the supply shaft, and detection means for detecting that the cleaning web is caught in the rotary member on the basis of a state of the signal output from the signal output means.